1. Field of the Invention
The present invention relates to an airbag inflatable with inflation gas.
2. Description of Related Art
JP8-104194 A discloses an airbag that includes a body cloth constituting a circumferential wall, a supplementary cloth applied to the inner surface of the body cloth for reinforcement or the like and an adhesive arranged between the body cloth and supplementary cloth for adhering the supplementary cloth to the body cloth. The airbag is manufactured only by adhesion and without sewing work.
JP6-227346 A discloses an airbag that includes a body cloth, a supplementary cloth and an adhesive used to heat-seal the supplementary cloth to the body cloth and is manufactured by sewing as well.
In the airbags disclosed in above two references, the adhesives are used solely to bond a supplementary cloth to the body cloth. The adhesives are not applied to other area than the area of the supplementary cloth, i.e., not used as a countermeasure against gas leakage of airbag.
JP 2004-218138 A teaches an airbag that is fabricated of a fabric having a layer of water-soluble or water-dispersible coating composition for reducing gas permeability. In this airbag, the coating composition is not used to bond a supplementary cloth to a body cloth.
Moreover, JP 10-129380 A discloses an airbag that is made of two pieces of body cloths each provided with a coating layer of unvulcanized rubber or thermo-plastic polyurethane for preventing gas leakage. The body cloths are coupled together by outer peripheral edges by bonding by vulcanization or heat sealing.
The airbag disclosed in this reference does not include a supplementary cloth. The coating layer is formed all over the body cloths, and thus increasing the weight of the base cloths. Further, if the coating is composed of rubber or polyurethane whereas the fabric forming the base cloths is formed of polyamide fiber, the difference of materials of the coating and fabric would make the airbag unrecyclable.
In this kind of airbag, to summarize, using the same coating composition both for bonding of supplementary cloths and prevention of gas leakage is expected to contribute to simplification of and cost saving in manufacturing of an airbag with means for preventing gas leakage. Specifically, prevention of gas leakage of the body cloth includes prevention of gas leakage through interstices of the texture of woven fabric and prevention of gas leakage caused by scorching and holing of a circumferential wall of the airbag due to hot mist droplets of inflation gas, or the like.
Moreover, reducing an application area of such coating would be desired for weight reduction whereas forming a base cloth of an airbag and coating applied thereto from the same type of material would be desirable from the viewpoint of recyclability.